Ocean Floor/Transcript
Transcript Text reads: The Mysteries of Life with Tim and Moby Tim and Moby are on a dock. Tim is standing. Moby is on his hands and knees at the end of the dock, looking down into the water. Tim reads from a typed letter. TIM: Dear Tim and Moby, Is it true that the tallest mountains on Earth are in the ocean? From, Dale. MOBY: Beep. Moby sticks his face in the ocean. A fish swims past. TIM: Well, it's pretty shallow here. But you can find the tallest mountains, deepest valleys, and flattest plains in the depths of the ocean. In fact, there's a lot going on below the ocean that we can't see. The continental shelf is the edge of a continent that extends out under water. An image shows a continental shelf in the depths of the ocean. TIM: On the Pacific coasts, the continental shelf is about ten to thirty kilometers long, but it's up to three hundred fifty kilometers on the Atlantic and gulf coasts. At the edge of the continental shelf we've got the continental slope. That's the end of the continent. An image shows the end of the continental shelf and the beginning of the continental slope, which plunges sharply downward. TIM: Beyond that, there are the trenches, valleys, plains, and ridges that make up the underwater landscape. An image shows a cross-section of the ocean floor, with the various features that Tim describes. Moby throws a floatation device into the ocean. The device drifts away. TIM: Currents cause changes in the sea floor by depositing sediment that fills in valleys and makes flat abyssal planes. An animation shows sediment settling on the ocean floor. TIM: Earth's plate movements cause the same sorts of surface changes underwater as they do on land. Where plates move apart, a new crust forms to fill in the gaps. When plates come together, or converge, one plate moves under the other and is destroyed. Converging plates form trenches. These oceanic trenches are much deeper than any valleys on dry land. Animations illustrate the plate movements and arrows show how plates move apart and converge and how crust and trenches form. TIM: Trenches are pretty active zones, where volcanos and earthquakes are likely to happen. And speaking of volcanos, you often find volcanic activity among mid-ocean ridges, which are underwater mountain chains that form when plates move apart. An animation shows an active underwater volcano. TIM: When volcanos erupt, hardened lava forms a new crust and a new sea floor. An animation shows what happens to lava. MOBY: Beep. TIM: Yeah, it's a cycle. Crust is destroyed in the trenches, and new crust forms at mid-ocean ridges. Sometimes volcanos will form underwater. These underwater volcanic cones are called seamounts. When seamounts get large enough, they poke out above the water's surface and form volcanic islands like Hawaii. An animation shows a growing seamount. It appears above the ocean's surface. An inset map shows the island state of Hawaii. MOBY: Beep. TIM: You want to move to Hawaii to surf? MOBY: Beep. TIM: Oh. You want to surf to Hawaii. That's, um, that's pretty much impossible. MOBY: Beep. Moby makes a surfer's hang-five sign. TIM: Whatever. Category:BrainPOP Transcripts